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Thermodynamic Properties of Binary and Ternary Mixtures ContainingDi-isopropyl Ether, 2-Propanol, and Benzene at T ) 313.15 K

R. M. Villamañán,† M. C. Martı́n,† M. A. Villamañán,† C. R. Chamorro,† and J. J. Segovia*

Research Group TERMOCAL, Dpto. Ingenierı́a Energética y Fluidomecánica, Escuela de Ingenierı́as Industriales Paseo del

Cauce 59, Universidad de Valladolid, E-47071 Valladolid, Spain

Vapor-liquid equilibrium data for the ternary system di-isopropyl ether (DIPE) + 2-propanol + benzeneand the binary system 2-propanol + benzene at T ) 313.15 K are reported. An isothermal total pressurecell has been used for the measurements. Experimental data have been correlated by Barker’s method usingthe Margules equation for the binary system and the Wohl expansion for the ternary system. The Wilson,nonrandom two-liquid (NRTL), and universal quasichemical activity coefficient (UNIQUAC) models havealso been applied for the calculations. A comparative study of the effect of the alcohol in mixtures containingDIPE or benzene is included, using the data previously published by the group.

Introduction

Ethers such as isopropyl ether, also known as di-isopropyl

ether or DIPE, are potential blending agents in the preparation

of the reformulated gasolines. Isopropyl ether is synthesized

from reactions between propene and 2-propanol which is also

obtained from the hydration of the propene. Therefore, the

synthesis of DIPE depends on the availability of propene.

Any process simulation of the synthesis, the purification, or

the gasoline blending prior to the design stage needs reliable

thermodynamic models for the description of the physical

behavior. The highest quality of thermodynamic data is required

to improve the interaction parameters of the predictive models

which are used in process simulation packages.

Our group is carrying out a research program of the

thermodynamic characterization of multicomponent mixtures

containing a different type of hydrocarbons (paraffins, cyclo-

paraffins, aromatics, oleffins) and ethers and alcohols as

oxygenated additives with the purpose of improving the

understanding and the model of the reformulated gasolines.

We performed a series of measurements of ternary mixtures

containing DIPE + alcohol + benzene which have been

published.1-4 Now, we report vapor-liquid equilibrium data

for the ternary system DIPE + 2-propanol + benzene and the

binary system 2-propanol + benzene both at 313.15 K; the other

two binary systems involved have been measured previously.5,6

Experimental Section Materials. All of the compounds were purchased from Fluka

Chemie AG and were of the highest purity available, chroma-

tography quality reagents (of the series puriss. p.a.) with a stated

purity by gas chromatography > 0.990 (GC area) for the DIPE

and > 0.995 (GC area) for the benzene and the 2-propanol. They

were degassed before measurements by a modified distillation

method based on the one suggested by Van Ness and Abbott. 7

The purities of the chemicals were also checked by gas

chromatography and were found to be > 0.995 (GC area) for

all of the compounds. The average value of the experimental

vapor pressures for the pure compounds is compared with those

reported in the literature as a check for complete degassing,

and the values are summarized in Table 1.

Apparatus and Procedure. A static vapor-liquid equilibrium

apparatus, consisting of an isothermal total pressure cell, has

been used for measuring the vapor-liquid equilibrium of the

binary and ternary mixtures. The apparatus and measuring

technique, based on that by Van Ness and co-workers,8,9 have

been described in a previous paper.10

Three positive displacement pumps of 100 mL capacity(model: Ruska 2200-801) were used to inject known volumes

of degassed components into a cell immersed in a high precision

water bath (model: Hart Scientific 6020) assuring a temperature

stability of ( 0.5 mK and thermostatted at T ) 313.15 K. The

pump resolution is 0.01 mL, and the resulting uncertainty in

the volume injected is ( 0.03 mL.

The cell with a capacity of 180 mL is provided with an

externally operated magnetic stirrer. Initially about 50 mL of

one component is injected into the evacuated cell, and the vapor

pressure is recorded. The second and third components are then

injected in appropriate proportions so as to achieve a desired

composition. The total mass injected is determined from the

* Corresponding author. Tel./fax: +34 983423756. E-mail: [email protected].† E-mail: [email protected]; [email protected]; [email protected]; [email protected].

Table 1. Average Values of Experimental Vapor Pressures ( pisat) for

the Pure Compounds Measured in this Work and Literature Values( pi

sat(lit.)), Molar Volumes of Pure Liquids (V iL), and the Second

Virial Coefficients ( Bii, B ij) at T ) 313.15 K Used for theCalculations

DIPE (i ) 1) 2-propanol (i ) 2) benzene (i ) 3)

pisat /kPa 37.108 13.897 24.386

pisat(lit.)/kPa 37.128a 13.902b 24.398a

37.090c 13.853d 24.341e

37.081d 13.895 f 24.380g

14.161e

V iL /(cm3 · mol-1)h 145 78 91

Bi1 /(cm3

· mol-1)i -1687.8 -1381.9 -1701.0 Bi2 /(cm

3· mol-1)i -1381.9 -1878.9 -871.0

Bi3 /(cm3

· mol-1)i -1701.0 -871.0 -1310.5

a Ref 6. b Ref 5. c Ref 24. d Ref 25. e Ref 22. f Ref 26. g Ref 27. h Ref 28. i Calculated by Hayden and O’Connell15 from Dymond and Smith.16

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value of 30.175 kPa. Also, we have found a few experimental

points of the system at the same conditions report by Storonkin

et al.23 They give lower maximum pressures than those reported

by Rhodes et al. A direct comparison of the experimental values

is shown in Figure 2, where the total pressure versus the mole

fraction of liquid and vapor phases is drawn.The composition and the pressure of the azeotrope have been

calculated using all of the models, and they are given in Table

4. The azeotrope is located at a benzene mole fraction of 0.7227,

and the corresponding pressure is 29.536 kPa, using the five-

parameter Margules equation.

The high positive deviation from the ideality behavior is also

shown with the values of the excess molar Gibbs energy

calculated with the Margules equation; a maximum of 1025

J · mol-1 is found for a benzene mole fraction of 0.55.

The ternary system DIPE (1) + 2-propanol (2) + benzene

(3) has been correlated using the same models and the Wohl

expansion. All of the models give similar values of the root-

mean-square deviation of the pressure; it ranges from 22 Pa for

the NRTL model to 47 Pa for the UNIQUAC model, and themaximum deviations range from (48 to 178) Pa for the same

Table 3. Total Pressure p for the Ternary System DIPE (1) +2-Propanol (2) + Benzene (3) at T ) 313.15 K and at VariousCompositions of the Liquid Phase x 1 and x 2 and the CalculatedVapor Phases y1 and y2 Using the Wohl Expansion

x 1 x 2 y1 y2 p /kPa

1.0000 0.0000 1.0000 0.0000 37.1090.7004 0.2996 0.8034 0.1966 37.1310.6767 0.2895 0.7742 0.1951 36.9520.6600 0.2823 0.7538 0.1941 36.7880.6257 0.2676 0.7124 0.1921 36.4340.5914 0.2529 0.6719 0.1902 36.074

0.5563 0.2379 0.6314 0.1883 35.7050.5218 0.2231 0.5924 0.1864 35.3310.4873 0.2083 0.5543 0.1844 34.9420.4529 0.1936 0.5170 0.1822 34.5530.4185 0.1789 0.4803 0.1797 34.1480.3873 0.1655 0.4475 0.1772 33.7620.3486 0.1490 0.4073 0.1736 33.2720.0000 1.0000 0.0000 1.0000 13.8950.3016 0.6984 0.6493 0.3507 30.6580.2944 0.6815 0.6148 0.3447 30.8000.2869 0.6642 0.5812 0.3386 30.9540.2709 0.6268 0.5153 0.3261 31.2140.2566 0.5937 0.4635 0.3160 31.3860.2416 0.5588 0.4150 0.3064 31.5020.2265 0.5239 0.3718 0.2979 31.5780.2114 0.4888 0.3330 0.2903 31.6000.1963 0.4539 0.2983 0.2834 31.595

0.1813 0.4190 0.2668 0.2771 31.5470.1663 0.3844 0.2383 0.2711 31.4780.1510 0.3490 0.2114 0.2650 31.3640.0000 0.0000 0.0000 0.0000 24.3750.3010 0.0000 0.4066 0.0000 29.5150.2938 0.0240 0.3787 0.0564 30.5440.2858 0.0505 0.3565 0.1001 31.2780.2714 0.0984 0.3296 0.1515 32.0000.2562 0.1490 0.3112 0.1853 32.2740.2407 0.2004 0.2978 0.2093 32.3250.2259 0.2497 0.2875 0.2272 32.2580.2106 0.3003 0.2782 0.2432 32.1000.1956 0.3503 0.2696 0.2580 31.8670.1809 0.3992 0.2613 0.2723 31.5790.1655 0.4504 0.2526 0.2877 31.2010.1505 0.5000 0.2438 0.3037 30.7561.0000 0.0000 1.0000 0.0000 37.1280.7164 0.0000 0.7787 0.0000 34.358

0.6983 0.0253 0.7453 0.0409 34.9430.6803 0.0504 0.7192 0.0725 35.3440.6422 0.1035 0.6791 0.1208 35.7520.6097 0.1489 0.6549 0.1496 35.8170.5726 0.2008 0.6338 0.1745 35.7150.5371 0.2503 0.6175 0.1937 35.5070.5011 0.3006 0.6031 0.2106 35.2010.4653 0.3505 0.5900 0.2263 34.8360.4296 0.4003 0.5773 0.2416 34.3920.3936 0.4506 0.5642 0.2576 33.8610.3580 0.5002 0.5506 0.2745 33.2470.0000 1.0000 0.0000 1.0000 13.8920.0000 0.7020 0.0000 0.4111 26.7180.0327 0.6790 0.0696 0.3927 27.4910.0580 0.6612 0.1200 0.3790 28.0750.0991 0.6323 0.1953 0.3580 28.9760.1520 0.5951 0.2806 0.3335 30.064

0.2001 0.5613 0.3481 0.3136 30.9740.2498 0.5264 0.4090 0.2953 31.8350.2993 0.4916 0.4625 0.2788 32.6320.3500 0.4561 0.5109 0.2635 33.3710.4002 0.4208 0.5539 0.2494 34.0420.4496 0.3861 0.5923 0.2364 34.6440.4998 0.3509 0.6283 0.2235 35.2030.0000 0.0000 0.0000 0.0000 24.3770.0000 0.2996 0.0000 0.2834 29.5150.0253 0.2920 0.0361 0.2753 29.8470.0562 0.2828 0.0786 0.2660 30.2510.1014 0.2692 0.1378 0.2533 30.8180.1524 0.2539 0.2007 0.2399 31.4310.1997 0.2397 0.2557 0.2282 31.9630.2521 0.2240 0.3134 0.2157 32.5270.3005 0.2095 0.3641 0.2046 33.0160.3499 0.1947 0.4136 0.1933 33.4920.4000 0.1797 0.4621 0.1820 33.949

0.4494 0.1649 0.5082 0.1706 34.3720.4998 0.1498 0.5541 0.1589 34.777

Table 4. Calculated Parameters of the Models Obtained for theBinary System Benzene (1) + 2-Propanol (2) at T ) 313.15 K,together with the Root-Mean-Square Deviation of Pressure (rms ∆ p)and the Maximum Value of the Deviation (max |∆ p|) a

Margules Wilson NRTL UNIQUAC

A12 1.4509 0.5469 1.6351 0.6271 A21 2.2095 0.1817 0.8188 0.8901

λ12 0.8271 λ21 1.9318η 1.2685

R 12 0.5634rms ∆ p /kPa 0.006 0.057 0.042 0.207max |∆ p|/kPa 0.010 0.154 0.107 0.527

x 1,azeotrope 0.7227 0.7175 0.7200 0.7071 pazeotrope /kPa 29.536 29.523 29.553 29.474

a The ∆ p term is defined as the difference between the experimentaland the calculated pressure.

Table 5. Calculated Parameters of the Models Obtained for theTernary System DIPE (1) + 2-Propanol (2) + Benzene (3) at T )313.15 K, together with the Root-Mean-Square Deviation of Pressure (rms ∆ p) and the Maximum Value of the Deviation (max|∆ p|) a

Wilson NRTL UNIQUAC Wohl

A12 0.6747 1.0802 0.3474 C 0 ) 2.9771

A21 0.3254 0.3924 1.4564 C 1 ) 0.4020 A13 0.3822 -0.5237 1.1660 C 2 ) -1.0078 A31 1.6639 0.8434 0.8082 A23 0.1965 0.8469 1.1436 A32 0.5300 1.5884 0.4113

R 12 0.4516

R 13 0.3000

R 23 0.5634rms ∆ p /kPa 0.030 0.022 0.047 0.029max |∆ p|/kPa 0.099 0.048 0.178 0.054

a The ∆ p term is defined as the difference between the experimentaland the calculated pressure.

Table 6. Calculated Parameters of the Margules Equation for theBinary Systems Involved in the Ternary System DIPE (1) +2-Propanol (2) + Benzene (3) at T ) 313.15 K, Used in the Wohl

Expansion

Aij A ji λij λ ji η

DIPE (i) + 2-propanol ( j)a 1.0988 1.4201 0.1902 0.4307DIPE (i) + benzene ( j)b 0.2134 0.1277 0.0282 0.02822-propanol (i) + benzene ( j) 2.2095 1.4509 1.9318 0.8271 1.2685

a Ref 5. b Ref 6.

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models. The ternary pressure surface is shown in Figure 3. In

general, the results obtained using the Margules equation and

the Wohl expansion are better than the other models, and the

Wilson model used to be the best of these semiempirical models.

The experimental values point out that the two azeotropes of maximum pressure, formed in the binary mixtures containing

the 2-propanol, disappear when the third component is added

to the mixture. The excess molar Gibbs energy was calculated

for the ternary system using the Wohl expansion, and the results

are presented graphically in Figure 4. It is shown that the highest

deviation from the ideality corresponds to the binary system

benzene + 2-propanol, as mentioned before.

Finally, a series of ternary systems containing DIPE +

benzene + alcohol has been studied, for the alcohols 1-butanol,4

2-butanol,3 isobutanol,1 1-propanol,2 and 2-propanol (presented

in this paper). All of the systems show a positive deviation from

the ideality. The excess molar Gibbs energies were calculated,

and in all of the systems the order of the highest values obtained

for the binary systems containing benzene + alcohol was thefollowing: 2-propanol > 1-propanol > isobutanol > 1-butanol >

2-butanol. The maximum values were obtained for a mole

fraction of benzene around 0.55. Those values range from (1025to 885) J · mol-1. Also, those binary mixtures (except for benzene

+ 1-butanol) exhibit a maximum pressure azeotrope.

The comparison of the binary mixtures DIPE + alcohol give

also quite high positive deviations from the ideality whose

excess molar Gibbs energies range from (586 to 771) J · mol-1

for a mole fraction of the ether around 0.55. The order for the

studied alcohols was the following: 2-propanol > 1-propanol >

2-butanol ∼ 1-butanol > isobutanol. Only the system DIPE +

2-propanol shows an azeotrope, and neither of the ternary

systems present an azeotrope.

Literature Cited

(1) Villamañán, R. M.; Chamorro, C. R.; Martı́n, M. C.; Segovia, J. J.Phase Equilibria Properties of Binary and Ternary Systems Containing

Figure 1. Pressure deviations ∆ p, defined as differences between experi-

mental and calculated pressures as a function of the liquid composition, x 1,

for the system benzene (1) + 2-propanol (2). [, this work; 4, Rhodes et

al.22

Figure 2. Total pressure at T ) 313.15 K of the binary system benzene

(1) + 2-propanol (2), as a function of the liquid, x 1, and vapor

composition, y 1. [, this work; 4, Rhodes et al.;22

/, Storonkin et al.23

Symbols represent the experimental points; lines are the calculations of

the Margules equation.

Figure 3. Oblique view of the pressure surface reduced by the Wohl

expansion for the ternary system DIPE (1)+

2-propanol (2)+

benzene (3)at 313.15 K.

Figure 4. Oblique view of the excess Gibbs energy surface surface reduced

by the Wohl expansion for the ternary system DIPE (1) + 2-propanol (2)

+ benzene (3) at 313.15 K.

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di-Isopropyl Ether plus Isobutanol plus Benzene at 313.15 K. Fluid Phase Equilib. 2006, 239, 178–182.

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Received for review November 16, 2009. Accepted April 2, 2010.Support for this work came from the Spanish Ministry of Scienceproject ENE2006-133 and from the Junta de Castilla y León referenceGR152.

JE900977E

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